The invention relates to a belt, especially a conveyer belt, and a method for manufacturing a belt.
Belts usually consist entirely or in large part of an elastic material with a proportionately high friction value (coefficient of friction). The high friction value is necessary in order to be able to transmit the greatest possible driving forces with the belt. Belts which are employed for conveying or transporting purposes, namely conveyer belts, are deflected along the conveying path by usually a rather large number of rollers or drums, thus being led around curves in the conveying plane. It has been established that disturbing noises arise in the regions where such a belt is deflected.
The objective of the invention is therefore to create a belt, especially a conveyer belt, which results in a lower level of noise being generated.
A belt which fulfills this objective has the features of claim 1. Accordingly, the outer side of the belt is provided at least partially with a reduced friction value. This embodiment of the belt according to the invention is based on the knowledge that the high friction value at the outer side of the material used in conventional belts causes relatively high-pitched and often disturbing noises when the belt is deflected. A solution to the objective on which the invention is based can be sufficiently achieved by providing a reduced friction value only to those outer surfaces of the belt which come into contact with the rollers or drums used to deflect the belt. Thus only part of the belt must be provided with a reduced friction value.
For a belt comprising a load-carrying traction means and at least one guidance means for directing the conveyer belt on the transport path, it is expedient to have only the guide means provided with a reduced friction value at least on part of its outer surface. This proves sufficient for reducing the generation of noise by the conveyer belt because the deflection of the conveyer belt along the conveying path occurs via a single or, if required, a plurality of guide means of the conveyer belt, with most of the disturbing noise being generated by this deflection. The traction means of the belt then requires no modification at all.
According to a preferred embodiment of the invention, a reduction of the friction value is achieved by an outer coating of at least one part of the belt using a material exhibiting a smaller friction value. This material is preferably made of a corresponding thermoplastic synthetic, such as polyamide, polypropylene or polytetrafluor ethylene. In contrast, the remaining material (core material) of the beltxe2x80x94apart from its reinforcement pliesxe2x80x94are made of elastic material, specifically rubber or an elastomer, in particular polyester elastomer or polyurethane, which has a greater friction value. The friction value of the core material can be up to twice as great as that of the coating material, in particular it is 20% to 50% greater.
The coating preferably takes place by means of a synthetic web applied externally to at least one part of the core material of the belt. This type of coating can be applied easily, ensuring a permanent bond with the core material of the belt. However, it is also conceivable to spray, flock coat or extrude the coating of synthetic material with a lower friction value onto the core material with a greater friction value.
According to a further development of the belt, a profile is to be given to at least the guide surfaces of the guide means. This profile can be formed by grooves and/or projections of an arbitrary cross-section. But it is also conceivable to have provided a web-like profile made of strands, in particular, criss-crossing strands. By giving a profile to at least the guide surfaces of the guide means, a reduction of the bearing surfaces on the rollers, drums or the like used to deflect the belt is achieved. In conjunction with the coating of reduced friction value, which in particular also extends across the region of the projections, grooves and/or strands, this arrangement results in a particularly effective reduction of unpleasant noises.
A method for solving the objective set forth above is disclosed by the measures of claim 17. Accordingly, the coating is first put into a form device for shaping at least one part of the belt, especially the guide means, then the remaining material for the belt, especially the core material, is put into the form device. The core material at least is put into the form device in a softened state so that during the subsequent profile fashioning of the belt with the coating material, the softened core forms a permanent bond. This method of coating the belt requires practically no additional effort. This additional effort is particularly negligible if the coating material is fed to the form device in a cold state. But it is also conceivable to have the coating material warmed.
According to a preferred development of the method, the preferably cold, or not free-flowing, coating material is put into a depression of the form device which corresponds to the shape of the belt of a part thereof, and is pre-shaped therein before the warmed core material for forming the remaining part of the belt or guide means is fed into the form device. Applying pressure to at least one part of the wall of the depression in the form device ensures that the coating is located at the designated position of what is later to become the belt or a part thereof, in particular in the designated regions at the outer side of the belt.